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Appendix VI.


heated on its way by contact with the uptake, and in at the ash-
grate space M to the fire N. The gaseous products then proceed
from N across the tubes c c to the uptake P p and funnel Q. Soot
doors are provided at RR, fire doprs at ss, and an equalising
pipe T T to a blow-off cock in the centre.

Pp. 831 and 918.    Automatic Feed-water Regulator.

A further example of this interesting contrivance is illustrated
in Fig. 949. Mr. Honeyball's invention has the merit of sim-
plicity, though involving the use of a pilot valve as in Mr.
Forster's regulator on p. 919. It was originally designed for
evaporators, or the small boilers which provide the make-up
steam in marine practice, but the principle can be equally well
applied to full-sized boilers. A vessel A is connected to the
boiler by the tube B in the steam space, and by c in the water
space. Attached to the vessel is a gun-metal clackbox or feed
check D E, and within this box are two valves, j K being a main
piston valve having a c woodite' face K, and L the pilot valve.
The latter is governed by the float N, and the lever M pivoted at P.
The feed water enters at F, and, passing through the orifices at G,
turns down by the pipe E to the boiler, the incoming pressure
lifting the piston J K, a loose fit in its chamber, for the purpose.
This kind of action goes on steadily until the float N has risen
high enough to free the valve L, which therefore closes. A curious
result follows the closing of L, for, whereas the piston j K has up
till now been lifted freely by the pressure, the rigid block of
water retained in the space from L to j positively resists any
attempt to move the piston, and not the smallest portion of water
is able to pass, the perfection of the temporary joint at K being
enhanced by the very slight elasticity of the woodite. If, how-
ever, the float falls, and opens the valve L ever so little, the feed
action recommences, and thus a delicate play occurs between
dosed and open that keeps a steady water level in the boiler.
' The diagram shews the closed condition, the supply being
automatically stopped till the water level has fallen. m